1. Field of Invention
The invention relates to an antenna structure and, in particular, to a multi-frequency antenna structure.
2. Related Art
The connections and communications among various wireless networks, such as wireless personal area networks (WPAN), wireless local area networks (WLAN), and wireless wide area networks (WWAN), or system devices can be implemented with the antennas therein.
Generally speaking the antennas of wireless devices can be external or internal. For example, the external antennas of some laptop computers are disposed at the top of the monitors or on the PCMCIA cards. Such external antennas have higher costs because they are exposed to the environment and more susceptible to damages. The other design is to embed antennas inside the laptop computers.
The internal antenna designs can avoid drawbacks of external antennas. For example, the computer device can have a better appearance. The antenna is also prevented from accidental damages. However, building the antenna inside a spatially limited computer device may have bad effects on its efficiency. Therefore, the internal antennas have to be appropriately designed in order to fit the space inside the portable computer device and to provide a sufficient efficiency.